Zooplankton Distribution in Coastal Water of the North-Western Bay of Bengal, Off Rushikulya Estuary, East Coast of India
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Indian Journal of Geo-Marine Sciences Vol. 44(4), April 2015, pp. 519-527 Zooplankton distribution in coastal water of the North-Western Bay of Bengal, off Rushikulya estuary, east coast of India *S. Srichandan, Biraja K. Sahu, R. Panda, S. K. Baliarsingh#, K. C. Sahu & R. C. Panigrahy Department of Marine Sciences, Berhampur University, Berhampur-760007, Odisha, India #(Present address) Indian National Centre for Ocean Information Services, Hyderabad-500090, India *[E-mail: [email protected]] Received ; revised Abstract In total, 186 species of holoplankton and 23 different types of meroplankton were encountered during this study. Zooplankton community was dominated by copepods represented by 112 species, belonging to 4 orders and 26 families. Calanoida emerged as the most dominant order among the copepods being comprised of 68 species. It was followed by poicilostomatoids with 26 species, cyclopoids with 10 species and harpacticoida with 8 species. Paracalanus aculeatus emerged as the most dominant species during pre-monsoon season while, Acrocalanus longicornis was dominant in monsoon and A. gibber in the post-monsoon season. Other dominant copepods were Oithona sp., Miracia efferata, Acartia southwelli, Centropages tenuiremis, Paracalanus parvus, Acrocalanus gracilis and Acartia erythraea. Average zooplankton density ranged from 2387 org./10m3 to 11659 org./10m3. Zooplankton volume ranged from 0.65 ml/10m3 in monsoon to 1.51 ml/10m3 in post- monsoon season. Despite high species abundance during premonsoon period, species diversity was maximum in monsoon. Species richness and dominance indices remained higher during post-monsoon whereas Pielou’s evenness (J’) was more in monsoon. Non-metric multidimensional scaling (MDS) ordinations based on Bray-Curtis similarities indicated that species composition was unequal during different months as there was no similarity above 40% level. [Keywords: Zooplankton, Copepod, Coastal water, Hydrography, Bay of Bengal] Introduction India has started in early 1900s5 and it gained momentum from 1950s and 1960s especially after Zooplankton constitutes a broad category and the IIOE. However, majority of studies were wide range of organisms in marine environment. 6 1 confined to areas like Cochin Back waters , Roman et al have opined that zooplankton are Mandovi and Zuari estuaries and their very important to marine pelagic ecosystems, that neighboring sea7, Vellar estuary and its adjoining support higher trophic levels and as the essential coastal water8 and Hooghly estuary9. Zooplankton determinant of the potential fishery yield. Several studies along Odisha coast in general remained microzooplankton species also constitute major meager and were limited to the Chilika lake10-12, food stuff of the larvae of crustaceans, molluscs Rushikulya estuary13, Bahuda estuary14, and fishes while some species of zooplankton are 15 16 2 Burhabalanga estuary , Mahanadi estuary . The used as water quality indicators and movement of 3 only study on zooplankton distribution in coastal water current . waters along the Odisha coast was that of Sahu et Therefore knowledge on species composition, al17. Present paper describes the seasonal abundance and distribution of zooplankton was variations in zooplankton species composition, always considered as great significance in marine population density and relative abundance of 4 ecological and fishery management exercises . In major groups in relation to variations in the recognition of the ecological and economic physico-chemical parameters of north-western significance of marine zooplankton, emphasis has Bay of Bengal, off the Rushikulya estuary. been laid to acquire more and more knowledge on species composition, seasonal abundance and Materials and Methods reproductive biology of marine and estuarine The present study was carried out in the Bay plankton worldwide leading to accumulation of a of Bengal, off Rushikulya estuary, south Odisha plethora of literature. Information relating to coast. Samples were collected from five stations zooplankton of coastal waters and estuaries in (Fig.1) at monthly interval from March 2010 to INDIAN J. MAR. SCI., VOL. 44, NO. 4 APRIL 2015 February 2011. This study area is influenced by estimated adopting the spectrophotometric fresh water flow via Rushikulya river which method given by Parsons et al20. receives high quantity of dissolved chemical Zooplankton samples were collected at each inputs from many sources including the effluent station by horizontal haul using a zooplankton net discharges of a Chloro-alkali plant. The (mesh size of 120 µm). A digital flow meter physiographic features, climate, tidal rhythms of 13,18 (Hydro Bios) was used to determine the volume the region etc have been discussed earlier . of water filtered. Samples collected from the Surface water samples were collected using a receiver were transferred to pre-cleaned polythene clean plastic bucket for measurement of bottles and preserved with 5% formaldehyde. In hydrographic parameters, nutrients and the laboratory, the zooplankton samples were first chlorophyll a. Water temperature (WT) and pH used for determination of plankton volume were recorded using mercury filled centigrade through volume displacement method. The thermometer and EUTECH field pH reader residual plankton on the filter paper was re- (accuracy ±0.01) respectively. Water samples for suspended in 5% formaldehyde and sub-sampling was made using Folsom plankton divider. Subsample was used for quantitative and qualitative analysis. Larger organisms like copepods of families Pontellidae, Eucalanidae, Euchaetidae, Chaetognaths, Dollioloids & Salps were sorted out and counted. Remaining mixture was made to exactly 100 ml and 1 ml of aliquot was transferred on to a Sedgwick–Rafter cell and observed under an inverted microscope (Cippon; Model No.21033) for identification and counting. Total number of macro and micro-zooplankton was taken as the population density. The numerical abundance was presented as org./10m3. Relative abundance was computed from the total density and the density of each group. Identification of zooplankton was done following standard literature21-23. Data were grouped into three seasons: premonsoon (PRM), monsoon (MON) and post- monsoon (POM). Analysis of Variance (ANOVA) test was performed to know the inter season comparison of different parameters. Correlation analysis was made to find out the possible relationships between different parameters and Fig.1. Map showing the sampling locations off Rushikulya estuary zooplankton density. Species diversity indices i.e. Marglef’s Species Richness (d), Pielou’s analysis of salinity, nutrients and chlorophyll a Evenness (J'), Shannon Wiener Diversity Index were collected in clean polyethylene bottles and (H' (loge)) and Simpson’s Dominance Index (λ) transported to the laboratory kept in an ice box. were determined using PRIMER (Plymouth Samples for dissolved oxygen (DO) analysis were Routines in Multivariate Ecological Research) fixed onboard with Winkler’s A and B solutions software Version 5. Zooplankton species and were transported to laboratory for further composition and abundance from March 2010 - analysis. DO was measured adopting Winkler’s February 2011 was analysed using nonparametric method, while salinity was estimated following 19 multivariate statistical methods in PRIMER Knudsen’s method . Water samples for nutrient Version 524,25 to decipher the similarity in species analysis were filtered against glass fiber filter composition. (GF/C) using Millipore Filtering System and were Results and Discussion analysed for nitrite (NO2–N), nitrate (NO3–N), ammonia (NH4–N), inorganic phosphate (PO4–P) Seasonally pooled mean and standard and silicate (SiO4–Si) following the procedures deviation values of the hydrographic parameters 19 described by Grasshoff et al . Chlorophyll a was and nutrients are given in Table 1. Each of the SRICHANDAN et al.: ZOOPLANKTON DISTRIBUTION IN COASTAL WATER hydrographic parameter such as water over the Bay of Bengal mainly depends on temperature (WT), salinity, pH and DO showed climatic variations especially the atmospheric well marked seasonal and spatial variations. conditions and rain fall26. Temperature variations Monthly collected data showed that water during the present study could also be ascribed to temperature varied from 21.8°C (station R-1, Jan) seasonal changes in atmospheric conditions and to 31.4°C (station R-4, May). Seasonally pooled rainfall. Monthly recorded salinity values ranged mean temperature values however ranged from from 25.3 PSU (station R-1, August) to 35.8 PSU 26.0°C to 28.9°C. Higher temperature was (station R-5, January). Seasonally pooled average recorded in PRM season while lower temperature salinity ranged from 30.58 PSU during MON was observed during POM months. Temperature season to 31.79 PSU during PRM period. Table 1. Variations of physicochemical and biological parameters St. WT pH DO Salinity NO2 NO3 NH4 PO4 SiO4 Chl-a ZooBio ZooPop (°C) (mg/L) (PSU) (µmol/L) (µmol/L) (µmol/L) (µmol/L) (µmol/L) (mg/ m3) (ml/10m3) (Org./10m3) PREMONSOON R-1 27.7 7.66 8.02 28.89 0.36 2.06 2.4 2.14 6.13 5.67 0.98 23054 R-2 28.3 7.97 7.78 29.7 0.32 1.66 2.47 1.25 4.72 2.51 1.39 11556 R-3 29.0 8.24 7.64 32.27 0.4 1.4 2.15 1.16 5.32 2.59 0.80 11234 R-4 29.6 8.29 7.86 33.26 0.27 0.93 1.37 0.91 5.02 1.59 1.37 8184 R-5 30.0 8.02 7.67 34.83 0.4 1.08 1.47 1.59 4.58 1.7 0.14 4270 Mean 28.9 8.04 7.79 31.79 0.35 1.43 1.97 1.41 5.15 2.81 0.93 11659 SED 1.0 0.25 0.15 2.47